TOKYO — For more than 65 years, the worst event in Japan’s modern history stood alone, with nothing afterward momentous enough to change its lessons. Those who survived the bombings of Hiroshima and Nagasaki decided that similar bombs should never be dropped again. To ensure that outcome, they called for the abolition of nuclear weapons.

Nuclear power, though, was another matter. Japan’s nationwide survivors’ group never rallied against nuclear-generated energy as such, perhaps because many saw a redemptive justice in using it peacefully. Reactors could power the country’s economy, they hoped, by harnessing the same force that once caused so much damage.

Then on March 11, the damage was reprised. The tsunami-triggered meltdowns at three Fukushima Daiichi nuclear reactors were nowhere near as acute or deadly as the cataclysm that engulfed Hiroshima. Still, in both cases, thousands of people were exposed to radiation. In both, thousands lost their homes. That is why, for Hiroshima survivor Akira Yamada, the bombings of 1945 no longer seem so final. Saturday is the 66th anniversary of the bombing of his city but the first on which he is also speaking out against civilian nuclear power.

“Yes, the events are connected,” Yamada said. “With both, I have regrets.”

Since the Fukushima crisis, Japan has launched a nationwide debate about the merits and risks of its atomic energy program. The most zealous anti-nuclear activists tend to speak of a history forsaken — as if, by racing to build reactors in the 1970s, the country had ignored the clear warning signs of Aug. 6 and Aug. 9, 1945.

But most of the bombing survivors, known as hibakusha, have long had a far more complex, and often positive, view of nuclear power — which partly explains why Japan now has reactors along almost every rural swath of its shoreline, 54 in all, accounting for about 30 percent of the national power supply.

Some hibakusha saw civilian nuclear energy as the antithesis of the destruction they had witnessed. Some even became nuclear power researchers, paving the way for nationwide acceptance of the technology.

In its charter documents, Nihon Hidankyo, Japan’s atomic bomb victims’ organization, called for the prevention of nuclear war and the elimination of nuclear weapons. But its statements about nuclear energy, even after the accidents at Chernobyl and Three Mile Island, were limited to occasional and unemphatic calls for better safety testing and research.

“Even though we’d gone through horrific experiences, nuclear power energy at that time was seen as the discovery of a second fire,” said Nagasaki survivor Sueichi Kido, 71. “In a way, we were hoping nuclear power could be used as a great tool to make our lives better.”

This June, three months into the nuclear emergency unfolding along the northeastern coastline, Hidankyo held its annual general assembly meeting in Tokyo. In previous years, Yamada said, the event had grown predictable: Survivors talked about their health and their friends who had died. Sometimes they shared details of an ongoing class-action lawsuit.

This time it was different. Roughly 120 survivors crowded into a conference room where they spent two days debating whether Hidankyo should call for a phaseout of nuclear power. An overwhelming majority, two attendees said, were in favor. But several survivors from Hiroshima spoke about the key role nuclear power plays in Japan’s economy. There was enough opposition to fuel a debate.

Yamada, 85, also felt conflicted. He’d moved in 1951 to Fukushima City, where he taught the history of economics at Fukushima University. In the 1960s he’d studied labor migration trends, and he noted how young students in the isolated parts of Fukushima prefecture were all but forced to take jobs in Tokyo. That changed with the construction, beginning in 1967, of the first nuclear reactor at Fukushima Daiichi.

As one of two representatives from Fukushima at the general assembly meeting, Yamada said, “I was in a difficult position.” About 30 bomb survivors still live in Hama-dori, near the plant, he said, and all were engaged in plant activities. It had sustained their careers, and their children’s. “They depended on that plant,” he said.

At the same time, he found the similarities between the meltdown and the bombings too striking to ignore. Sixty-six years ago a bomb had blown the shingles off the roof of his house, and he’d climbed up there to see “a fireball swallowing the entire city.” Now he was living 40 miles from the exploding buildings at a nuclear plant, and he felt compelled to urge local authorities to grant full lifetime medical treatment to those who were exposed.

“People who have been through radiation exposure of any kind — they all have the same risks,” Yamada said. “It’s consistent with the ideas of Hidankyo to speak out.”

That’s what Hidankyo decided to do. After the June 8 meeting, Terumi Tanaka, the organization’s secretary general, called for the decommissioning of reactors that had already been shut down for inspections. A month later, after an executive meeting, the group called for first time for the “elimination of nuclear power generation.”

Kido, the Nagasaki survivor, called it a “historical transition.” But he regretted that the group hadn’t made the change earlier, in time to prevent a new horror.

“To me, we’ve created the third hibakusha,” Kido said. “The first hibakusha was people in Nagasaki and Hiroshima. The second hibakusha was created with the Bikini Atoll hydrogen bomb testing [in 1954]. The third hibakusha is created with the accident at Fukushima Daiichi plant.”